The present invention relates to cutting tools in general, and more particularly to such metal cutting tools as drills, reamers, and the like, in which an insert with two opposite blades having cutting edges is employed. Even more specifically, the invention pertains to a cutter insert or assembly which is inserted into a transverse slot provided in a drill bar.
Drill inserts have been known, which include a housing and two diametrically oppositely positioned cutters having cutting edges extended outwardly from the elongated housing at two opposite ends thereof. The housing of the insert is provided in the middle thereof with a prismatic notch, in which the tapered end of an axial adjustment pin for limiting a floating motion of the insert in a radial direction of the drill bar, is more or less engaged, and the cutters inserted into the elongated recess of the housing are adjusted to each other along that elongated recess by means of a central adjustment bolt which has a conical tip with the inclined adjustment surfaces which abut against the respective inner ends of the cutters, positioned within that recess. After the cutters have been adjusted to each other in the elongated recess of the insert housing they are secured in that housing by means of clamping bolts.
The cutting assembly or insert of the type under discussion has been disclosed in German patent DE-PS 24 36 501. The drill bar insert described in this patent is utilized as a fine drill cutter for making holes with narrow allowances, specifically for automatic drills which operate with high speeds.
Each cutter in the known drill bar insert includes a cutter carrier, which is supported in the housing of the insert and is extended outwardly therefrom, and a cutter plate soldered to the cutter carrier. This construction has the disadvantage that various sizes of the cutters must be provided for various ranges of diameters of the holes to be drilled. Such cutters of narrow sizes, however, because of high costs, can not be made as one-piece of high strength material.
Another cutting tool assembly is disclosed in U.S. Pat. No. 2,680,390. A bar for an adjustable reamer is described in this patent which bar has a pair of blades and a blade holder therefor adapted as a unit to be positioned in the transverse slot in the bar and locking set screws in the side walls of the blades to lock the same against relative movement with the holder. The rear end faces of the cutters form a complementary inclined notch to receive the forward inclined head of a centering pin disposed within the axial bore of the bar behind the cutter blade assembly. The centering pin has a radially reduced shank portion to receive a collar of flexible deformable material between it and the bar to permit floating of the blade assembly but resiliently resist radial displacement thereof in the bar. A pressure pin assembly is disposed within the bore behind the centering pin and is provided with externally accessible adjustment and locking screws adapted to apply axial forces upon the pressure pin to force the centering pin axially forwardly for controlling the position of the centering pin.